RESUMO
Demand for biopesticides is growing due to the increase of areas under integrated pest management worldwide. Conidia from entomopathogenic fungi play a major role as infective units in the current market of biopesticides. Success in a massive production of fungal conidia include the use of proper long-term conservation microbial methods, aimed at preserving the phenotypic traits of the strains. The development of suitable inoculants should also be considered since that favours a rapid germination and invasiveness of the substrate in solid state cultures (SSC). After the selection of a suitable fungal strain, proven optimization approaches for SSC mainly include the combination of substrates, moisture, texturizers, aeration and moderate stress to induce conidiation. Nonetheless, during storage and upon application in open fields, conidia either as free propagules or imbibed in formulations are subjected to stress due to abiotic factors, then quality should be preserved to resist such harsh conditions. All of these topics are analysed in this report.
Assuntos
Fungos/fisiologia , Insetos/microbiologia , Esporos Fúngicos/crescimento & desenvolvimento , Animais , Agentes de Controle Biológico/metabolismo , Meios de Cultura/farmacologia , Fungos/efeitos dos fármacos , Fenótipo , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/metabolismo , Estresse Fisiológico , Especificidade por SubstratoRESUMO
BACKGROUND: In addition to high production levels of conidia, the success of entomopathogenic fungi as biological control agents depends both on their prevalence under the environmental conditions found in open fields (resistance to stress) and on the capacity of these conidia to infect pests. This study compares conidium production, infectivity and resistance to thermal and osmotic stress in two strains of Isaria fumosorosea (ARSEF 3302 and CNRCB1) grown either under a normal atmosphere (21% O2) or using enriched oxygen pulses (26% O2). RESULTS: After 180 h, the ARSEF 3302 strain with 26% O2 pulses increased conidium production nearly fivefold compared with the normal atmosphere, while conidium production by the CNRCB1 strain decreased by 50% under O2 pulses, relative to the values measured with the normal atmosphere. The conidia obtained with 26% O2 pulses had a greater germination rate and resistance to thermal and osmotic stress, in addition to improved infectivity against Galleria mellonella (Lepidoptera) larvae. These findings were associated with an increase in catalase activities for both strains. CONCLUSION: An enriched oxygen atmosphere increases the quality of conidia of both strains of I. fumosorosea, with a variable effect on conidium production.